1. Field of the Invention
The present invention relates to a digital-analog converter capable of easily extending the resolution, and more particularly, to a digital-analog converter capable of easily extending the resolution that can easily extend the resolution by a simple circuit implementation when a 10-bit digital-analog converter is configured on the basis of an 8-bit digital-analog converter used in a display driving IC, and prevent an increase in area of the display driving IC.
2. Description of the Related Art
In recent years, the market for display devices, especially, digital TVs has grown. In order to achieve high display quality, high output resolution of driving ICs of the display devices has been required.
In general, bit extension of the digital-analog converter used in the driving IC is performed to increase the output resolution of the driving IC.
FIG. 1A is a configuration view illustrating an example of a digital-analog converter according to the related art.
Referring to FIG. 1A, a digital-analog converter 10 according to the related art includes a first resistor array 11 that divides voltages by a plurality of resistors, a first switch array 12 that has a plurality of switches for selecting the divided voltages, a first buffer unit 13 that buffers the two voltages selected by the first switch array 12, a second resistor array 14 that divides the voltages buffered by the first buffer unit 13 by a plurality of resistors, a second switch array 15 that selects the voltages divided by the second resistor array 14, a decoder unit 16 that controls the operation of selecting the voltages by each of the first switch array 12 and the second switch array 15, and a second buffer unit 17 that buffers the voltages selected by the second switch array 15 to output a final output voltage.
The above-described digital-analog converter 10 according to the related art is obtained by adding the first buffer unit 13, the second resistor array 14, and the second switch array 15 to a converter with 8-bit resolution. However, problems occur with the bit extension in that an increase in the number of resistors and switches results in an increase of chip area, and an off-set voltage of the buffer unit is applied to the final output voltage to cause deterioration in off-set characteristics of the entire system.
FIG. 1B is a configuration view illustrating another example of a digital-analog converter according to the related art.
Referring to FIG. 1B, a digital-analog converter 20 according to the related art includes a first resistor array 21 that divides voltages by a plurality of resistors, a first switch array 22 that selects the voltages divided by the first resistor array 21 by a plurality of switches, a second resistor array 23 that divides the voltages divided by a plurality of resistors, a second switch array 24 that selects the voltages divided by the second resistor array 23 by a plurality of switches, a decoder unit 25 that controls the operation of selecting the voltages by the first switch array 22 and the second switch array 24, and a buffer unit 26 that buffers the voltages selected by the second switch array 24.
When compared with the digital-analog converter 10 according to the related art, which is shown in FIG. 1A, the digital-analog converter 20 according to the related art increases a plurality of resistances of the plurality of resistors that are included in the second resistor array 23 to thereby remove the first buffer unit 13. However, the second resistor array 23 and the second switch array 24 are added to extend the resolution of the digital-analog converter with 8-bit resolution. The addition of the second resistor array 23 and the second switch array 24 results in an increase in the number of resistors and switches. This increase results in an increase of chip area. Further, since the resistances of the resistors included in the second resistor array 23 are increased, a current loss may occur to reduce uniformity between output channels.